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Choroidal perfusion measurements usi...

Wu, Frank Iway.

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Choroidal perfusion measurements using optical coherence tomography.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Choroidal perfusion measurements using optical coherence tomography./
作者:	Wu, Frank Iway.
面頁冊數:	119 p.
附註:	Source: Dissertation Abstracts International, Volume: 65-01, Section: B, page: 0316.
Contained By:	Dissertation Abstracts International65-01B.
標題:	Engineering, Biomedical. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3118635

Choroidal perfusion measurements using optical coherence tomography.
Wu, Frank Iway.

Choroidal perfusion measurements using optical coherence tomography. - 119 p.

Source: Dissertation Abstracts International, Volume: 65-01, Section: B, page: 0316.

Thesis (Ph.D.)--Northwestern University, 2003.

The importance of choroidal blood flow in relation to ocular diseases is only beginning to be fully appreciated. Long standing beliefs about the choroid, e.g., an overperfused tissue and nonautoregulatory behavior, are beginning to be dispelled with better flow measurement techniques and experimental protocols. Existing choroidal blood flow measurement techniques all have their limitations, e.g., invasiveness and limited measurement repeatability of microsphere injection and angiography techniques. The laser Doppler flowmetry technique shows great promise because of its accepted mathematical model and potential of noninvasive measurements, however, it is limited to regions, or animals, with no retinal circulation to prevent signal contamination because the coherent laser results in a large scanning voxel of approximately 1 mm3. A relatively new technique of using partially coherent light with optical ranging, called Optical Coherence Tomography (OCT), provides imaging capabilities conceptually similar to ultrasound with approximately 15 mum axial resolution in biological tissue. Two Doppler OCT techniques were used in an attempt to measure choroidal blood flow in ablino rats. Color Doppler OCT proved capable of detecting blood flow in choroidal vessels down to approximately 80 mum but incapable of detecting blood flow in the choriocapillaris because of insufficient velocity resolution. The second Doppler technique, phase-resolved OCT, afforded a two orders of magnitude increase in velocity resolution but an almost 90° incident angle between the beam and velocity direction made velocity detection in the choriocapillaris unreliable. However, the amplitude modulation of the rat choroid from sequential axial scans was found to fluctuate, and the fluctuation frequency was hypothesized to be indicative of choroidal blood flow. In order to obtain data sets with a range of choroidal blood flow, sequential axial scans were taken under different physiological conditions including a range of intraocular pressures from 15 mmHg to 120 mmHg; before, during, and after clamping the common carotid arteries which are the main supply to the ophthalmic arteries; and after sacraficing the rat. Numerous analysis techniques were attempted on the data sets, and a simple amplitude differencing technique was found to provide the best potential indicator of choroidal perfusion. The inability of Doppler OCT to detect capillary bed blood flow coupled with the speckle differencing indicator's matching trend of the expected choroidal blood flow to the physiological insults suggests that methods of counting statistics, as opposed to the traditional Doppler techniques, are more appropriate for the quantification of tissue perfusion using the OCT imaging paradigm.Subjects--Topical Terms:

1017684
Engineering, Biomedical.

Choroidal perfusion measurements using optical coherence tomography.
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520 $a The importance of choroidal blood flow in relation to ocular diseases is only beginning to be fully appreciated. Long standing beliefs about the choroid, e.g., an overperfused tissue and nonautoregulatory behavior, are beginning to be dispelled with better flow measurement techniques and experimental protocols. Existing choroidal blood flow measurement techniques all have their limitations, e.g., invasiveness and limited measurement repeatability of microsphere injection and angiography techniques. The laser Doppler flowmetry technique shows great promise because of its accepted mathematical model and potential of noninvasive measurements, however, it is limited to regions, or animals, with no retinal circulation to prevent signal contamination because the coherent laser results in a large scanning voxel of approximately 1 mm3. A relatively new technique of using partially coherent light with optical ranging, called Optical Coherence Tomography (OCT), provides imaging capabilities conceptually similar to ultrasound with approximately 15 mum axial resolution in biological tissue. Two Doppler OCT techniques were used in an attempt to measure choroidal blood flow in ablino rats. Color Doppler OCT proved capable of detecting blood flow in choroidal vessels down to approximately 80 mum but incapable of detecting blood flow in the choriocapillaris because of insufficient velocity resolution. The second Doppler technique, phase-resolved OCT, afforded a two orders of magnitude increase in velocity resolution but an almost 90° incident angle between the beam and velocity direction made velocity detection in the choriocapillaris unreliable. However, the amplitude modulation of the rat choroid from sequential axial scans was found to fluctuate, and the fluctuation frequency was hypothesized to be indicative of choroidal blood flow. In order to obtain data sets with a range of choroidal blood flow, sequential axial scans were taken under different physiological conditions including a range of intraocular pressures from 15 mmHg to 120 mmHg; before, during, and after clamping the common carotid arteries which are the main supply to the ophthalmic arteries; and after sacraficing the rat. Numerous analysis techniques were attempted on the data sets, and a simple amplitude differencing technique was found to provide the best potential indicator of choroidal perfusion. The inability of Doppler OCT to detect capillary bed blood flow coupled with the speckle differencing indicator's matching trend of the expected choroidal blood flow to the physiological insults suggests that methods of counting statistics, as opposed to the traditional Doppler techniques, are more appropriate for the quantification of tissue perfusion using the OCT imaging paradigm.
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